Offer baseline `RavenwoodFlagsValueProvider`.

Many test authors are starting to use `CheckFlagsRule` across suites
like CTS, so instead of recommending that they use `null` when on
Ravenwood, offer them a clear behavior that is either "all-on" or
"all-off".

Eventually we'll explore providing default flag values on Ravenwood,
but let's get something cleaner available now.

Bug: 318841620
Test: ./frameworks/base/ravenwood/run-ravenwood-tests.sh
Change-Id: Id234a375426fad38f64d3a999339bb720eae84bf

Ravenwood.bp

@@ -205,8 +205,10 @@ android_ravenwood_libgroup {
         // Provide runtime versions of utils linked in below
         "junit",
         "truth",
+        "flag-junit",
         "ravenwood-framework",
         "ravenwood-junit-impl",
+        "ravenwood-junit-impl-flag",
         "mockito-ravenwood-prebuilt",
         "inline-mockito-ravenwood-prebuilt",
     ],
@@ -220,6 +222,7 @@ android_ravenwood_libgroup {
     libs: [
         "junit",
         "truth",
+        "flag-junit",
         "ravenwood-framework",
         "ravenwood-junit",
         "mockito-ravenwood-prebuilt",

core/tests/coretests/src/android/os/PowerManagerTest.java

@@ -32,6 +32,7 @@ import android.platform.test.annotations.IgnoreUnderRavenwood;
 import android.platform.test.annotations.RequiresFlagsEnabled;
 import android.platform.test.flag.junit.CheckFlagsRule;
 import android.platform.test.flag.junit.DeviceFlagsValueProvider;
+import android.platform.test.flag.junit.RavenwoodFlagsValueProvider;
 import android.platform.test.ravenwood.RavenwoodRule;
 
 import androidx.test.InstrumentationRegistry;
@@ -86,7 +87,8 @@ public class PowerManagerTest {
 
     // Required for RequiresFlagsEnabled and RequiresFlagsDisabled annotations to take effect.
     @Rule
-    public final CheckFlagsRule mCheckFlagsRule = RavenwoodRule.isUnderRavenwood() ? null
+    public final CheckFlagsRule mCheckFlagsRule = RavenwoodRule.isOnRavenwood()
+            ? RavenwoodFlagsValueProvider.createAllOnCheckFlagsRule()
             : DeviceFlagsValueProvider.createCheckFlagsRule();
 
     /**

core/tests/coretests/src/android/os/WorkDurationUnitTest.java

@@ -22,6 +22,7 @@ import android.platform.test.annotations.IgnoreUnderRavenwood;
 import android.platform.test.annotations.RequiresFlagsEnabled;
 import android.platform.test.flag.junit.CheckFlagsRule;
 import android.platform.test.flag.junit.DeviceFlagsValueProvider;
+import android.platform.test.flag.junit.RavenwoodFlagsValueProvider;
 import android.platform.test.ravenwood.RavenwoodRule;
 
 import androidx.test.runner.AndroidJUnit4;
@@ -40,7 +41,8 @@ public class WorkDurationUnitTest {
 
     // Required for RequiresFlagsEnabled and RequiresFlagsDisabled annotations to take effect.
     @Rule
-    public final CheckFlagsRule mCheckFlagsRule = RavenwoodRule.isUnderRavenwood() ? null
+    public final CheckFlagsRule mCheckFlagsRule = RavenwoodRule.isOnRavenwood()
+            ? RavenwoodFlagsValueProvider.createAllOnCheckFlagsRule()
             : DeviceFlagsValueProvider.createCheckFlagsRule();
 
     @Before

ravenwood/Android.bp

@@ -86,6 +86,21 @@ java_library {
     jarjar_rules: ":ravenwood-services-jarjar-rules",
 }
 
+// Separated out from ravenwood-junit-impl since it needs to compile
+// against `module_current`
+java_library {
+    name: "ravenwood-junit-impl-flag",
+    srcs: [
+        "junit-flag-src/**/*.java",
+    ],
+    sdk_version: "module_current",
+    libs: [
+        "junit",
+        "flag-junit",
+    ],
+    visibility: ["//visibility:public"],
+}
+
 // Carefully compiles against only test_current to support tests that
 // want to verify they're unbundled.  The "impl" library above is what
 // ships inside the Ravenwood environment to actually drive any API
@@ -95,10 +110,12 @@ java_library {
     srcs: [
         "junit-src/**/*.java",
         "junit-stub-src/**/*.java",
+        "junit-flag-src/**/*.java",
     ],
     sdk_version: "test_current",
     libs: [
         "junit",
+        "flag-junit",
     ],
     visibility: ["//visibility:public"],
 }

ravenwood/junit-flag-src/android/platform/test/flag/junit/RavenwoodFlagsValueProvider.java

+/*
+ * Copyright (C) 2024 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package android.platform.test.flag.junit;
+
+import android.platform.test.flag.junit.CheckFlagsRule;
+import android.platform.test.flag.junit.IFlagsValueProvider;
+
+/**
+ * Offer to create {@link CheckFlagsRule} instances that are useful on the Ravenwood deviceless
+ * testing environment.
+ *
+ * At the moment, default flag values are not available on Ravenwood, so the only options offered
+ * here are "all-on" and "all-off" options. Tests that want to exercise specific flag states should
+ * use {@link android.platform.test.flag.junit.SetFlagsRule}.
+ */
+public class RavenwoodFlagsValueProvider {
+    /**
+     * Create a {@link CheckFlagsRule} instance where flags are in an "all-on" state.
+     */
+    public static CheckFlagsRule createAllOnCheckFlagsRule() {
+        return new CheckFlagsRule(new IFlagsValueProvider() {
+            @Override
+            public boolean getBoolean(String flag) {
+                return true;
+            }
+        });
+    }
+
+    /**
+     * Create a {@link CheckFlagsRule} instance where flags are in an "all-off" state.
+     */
+    public static CheckFlagsRule createAllOffCheckFlagsRule() {
+        return new CheckFlagsRule(new IFlagsValueProvider() {
+            @Override
+            public boolean getBoolean(String flag) {
+                return false;
+            }
+        });
+    }
+}

ravenwood/test-authors.md

@@ -112,6 +112,24 @@ public class MyCodeTest {
 
 This naturally composes together well with any `RavenwoodRule` that your test may need.
 
+While `SetFlagsRule` is generally a best-practice (as it can explicitly confirm behaviors for both "on" and "off" states), you may need to write tests that use `CheckFlagsRule` (such as when writing CTS).  Ravenwood currently supports `CheckFlagsRule` by offering "all-on" and "all-off" behaviors:
+
+```
+import android.platform.test.flag.junit.CheckFlagsRule;
+import android.platform.test.flag.junit.DeviceFlagsValueProvider;
+import android.platform.test.flag.junit.RavenwoodFlagsValueProvider;
+import android.platform.test.ravenwood.RavenwoodRule;
+
+@RunWith(AndroidJUnit4.class)
+public class MyCodeTest {
+    @Rule
+    public final CheckFlagsRule mCheckFlagsRule = RavenwoodRule.isUnderRavenwood()
+            ? RavenwoodFlagsValueProvider.createAllOnCheckFlagsRule()
+            : DeviceFlagsValueProvider.createCheckFlagsRule();
+```
+
+Ravenwood currently doesn't have knowledge of the "default" value of any flags, so using `createAllOnCheckFlagsRule()` is recommended to verify the widest possible set of behaviors.  The example code above falls back to using default values from `DeviceFlagsValueProvider` when not running on Ravenwood.
+
 ## Strategies for migration/bivalent tests
 
 Ravenwood aims to support tests that are written in a “bivalent” way, where the same test code can be dual-compiled to run on both a real Android device and under a Ravenwood environment.